Cold Liquids Fed to Preterm Infants: Efficacy and Safety After 10 Minutes of Exposure

Swallowing dysfunction, medically defined as dysphagia, commonly occurs in infants born
prematurely due to inadequate timing and coordination of the sensorimotor sequences required
for safe swallowing. Approximately 70% of prematurely born infants will be diagnosed with
oral, pharyngeal and/or esophageal phase dysphagia with an inverse relationship between
severity and gestational age at birth.(1)

Swallowing is extremely important for the infant and child to meet the nutritional
requirements for growth and development. When swallowing is dysfunctional, the consequences
can be devastating for the infant, possibly resulting morbidity, with complications including
pneumonia, respiratory disease, growth compromise or failure to thrive.(1-6) The implications
of swallowing difficulty are, therefore, of considerable medical importance to the medical
team working with these infants.

A videofluoroscopic swallow study (VFSS) is a widely used assessment for the diagnosis of
neonatal dysphagia. VFSS is a definitive investigation to objectively assess the adequacy of
airway protection during swallowing and allows simultaneous viewing of the bolus as it passes
through the oral, pharyngeal and esophageal stages of swallowing.(7) For infants feeding from
a bottle, the clinician relies on the VFSS to both identify and correct the swallowing
dysfunction. Several therapeutic techniques or modifications are used during a VFSS to
improve swallowing safety in infants, such as various nipple flow rates,(8,9) feeding
positions,(10) or pacing the infant's sucking bursts.(11) The most frequently used
modification is to thicken the infant's formula or breastmilk to a thicker
consistency,(12-14) however, thickening causes some difficulty making it an undesirable
option for young infants treated in the neonatal intensive care unit (NICU).(15) These
difficulties have resulted in clinicians using alternate therapeutic techniques to treat
dysphagia neonates. One alternate technique is to feed the infant cold liquids to stimulate a
safer swallow.(16-20)

Original findings obtained by these investigators was the first to indicate that cold liquid
swallows reduce airway compromise in dysphagic preterm infants when compared to room
temperature liquid. Specifically, the occurrence of deep penetration (p=0.029), aspiration
(0.017), mild penetration (p=0.044) and nasopharyngeal reflux (p=0.006) decreased
significantly in the cold swallow (CS) condition when compared to the room temperature
swallow (RTS) condition during VFSS. Similar findings are documented in adults with
dysphagia.(21-35) These positive effects are theorized to occur due to the cold liquid
providing the sensory receptors within the pharynx increased sensory information which
triggers more efficient swallowing movements.(12,13,21-23)

The original study assessed 5 cold liquid swallows, which provided important information
regarding the immediate effects of cold liquids on the pharyngeal swallowing mechanism in
preterm infants with dysphagia. Further information regarding the duration of these positive
effects is necessary to prove its reliability as a modification to be used at bedside. This
study is designed to assess the swallowing mechanism of dysphagic preterm infants after
feeding cold liquids for 10 minutes to objectively identify any changes over time.

In addition to the paucity of evidence regarding improved swallowing function over time, the
safety of feeding cold liquids remains questionable in the preterm infant population. The
greatest concern for these infants is the development of cold stress or altered digestive
functioning due to the cold temperature of the liquid. The effects of cold stress in infants
are observed in all body systems, including cool skin, tachypnea, respiratory distress,
desaturation, increasing episodes of apnea and bradycardia, increased gastric residuals, and
emesis.(36) Several older studies have assessed the effects of cold feeds in healthy term and
healthy pre term infants, however, study populations may not be representative of todays
preterm infant population due to significant medical advances and increased survival rates of
extremely preterm infants.

Holt and colleagues(37) found no difference in sleep pattern, vocalizations, motility,
intake, feeding behavior, weight gain, temperature or regurgitation in preterm infants with a
weight of >1,500gm, when fed cold formula. Gonzalez and colleagues(38) found no significant
differences in axillary temperature or gastric residuals in preterm infants fed cold (0-4°C)
verses room temperature (25°C) milk. Participants included 14 preterm infants with a
gestational age at birth (GAB) of 28-30w, and a mean corrected gestational age of 32 weeks.
Anderson and Berseth(39) found no differences in infants' antral or duodenal motor activity
as assessed via manometry, as well as gastric emptying among cold (6°C), room temperature
(24°C), or body temperature (37°C) feeding groups. This study included preterm infants with
GAB 25-36weeks, mean birth weights 915-2,455g. Corrected gestational age of 32-36 weeks at
the time of the study. Feedings were given in random order for 3 liquid temperatures. Across
all temperatures they found that all infants emptied approximately one third of the bolus
feeding by 20 minutes. And across all temperatures approximately 10-20% of the bolus feeding
remained in their stomach 2 hours post-prandially. The authors propose that thermo-receptors
within the gastrointestinal tract do not appear to be functional in this age group.

Blumenthal and colleagues(40) found no statistical differences between stomach emptying rate
in cold (0-4°C), room temperature (25°C) or body temperature (37°C) formula in 20 healthy
preterm infants with a mean birth weight of 2.75 ± 0-18 (range 1.49-3.38) kg, and gestation
37-7 ± 0.6 (range 34-41) weeks. They also reported that in all infants the cold feeds were
well tolerated and produced no obvious clinical effects.

To assess the potential risks of cold stress, each participant's body temperature will be
obtained pre and post cold liquid exposure. To assess digestive functioning, the temperature
of each participant's gastric contents will be obtained pre and post cold liquid exposure by
extraction of the gastric content via a naso-gastric tube (NGT). If the child does not have a
naso-gastric tube in place at the time of the study, the subjects will be enrolled but no
documentation of the stomach content temperature will be obtained.

Inclusion Criteria:

- Infants born prematurely, as defined by birth at less than 37 weeks gestational age,
referred for a videofluoroscopic swallow study (VFSS) due to suspected pharyngeal
phase dysphagia.

Exclusion Criteria:

- Infants born prematurely with a corrected gestational age of 43 weeks or greater.